Cathode structure for electric discharge devices



June 7, 1949. J. H. HUTCHINGS 2,472,077

CATHODE STRUCTURE FOR ELECTRIC DISCHARGE DEVICES Filed March 27, 1945 Patented June 7, 1949 CATHODE STRUCTURE FOR ELECTRIC DISCHARGE DEVICES John H. Hutchings, Geneva, 111., assignor to Continental Electric Company, Geneva, 11]., a corporation of Illinois Application March 27, 1945, Serial No. 585,029

17 Claims.

This invention relates to improvements in electric discharge devices, more particularly of the type of full wave gas filled rectifiers.

Such rectifiers employ two anodes for flow of current alternately between the respective anodes and the cathode on different parts of the cycle. As constructed heretofore, these have presented difiiculties due to cross current, namely, the current that flows to the negative anode while the positive anode is conducting.

An object of this invention is to eliminate substantially the cross current in the tube by separating the flow of current to the respective anodes, so that the respective operations thereof are maintained entirely separate and without conflict therebetween.

This object is accomplished by providing a cathode assembly enclosed Within a shield or casing which has an opening to one of the anodes that is oifset from the opening provided for the other anode, so these are out of communication with each other and out of direct alignment. Moreover, the cathode assembly is separated into parts designed for flow of current to the respectiv anodes to facilitate the elimination of cross current therebetween.

A further object of the invention is to improve the construction of the cathode assembly as to simplicity, the ability to withstand vibration and bumping or jarring, and with a low rate of gas clean-up.

This object is accomplished by the mounting of the cathode assembly in a shield or casing in which the cathode is made in two parts and separated by an insulating washer which serves to separate the top half from the bottom half of the cathode shield or casing, but which provides for the conducting of the filament current between the sections of the cathode, accordin to the preferred embodiment of the invention.

This preferred embodiment is illustrated in the accompanying drawings in which:

Fig. 1 is a side elevation of an electrical discharge tube in which the improved structure is provided, with a part broken away and in section;

Fig. 2 is an enlarged side elevation of the filament structure of the cathode;

Fig. 3 is a side elevation of the cathode shield or casing;

Fig. 4 is a similar view at right angles thereto;

Fig. 5 is a bottom plan view thereof; and

Fig. 6 is a perspective view of one of the spacer shields detached.

Referring to Fig. 1, the electric discharge device in which this invention is illustrated com prises an enclosed vessel I, usually of tubular form and constructed in the form of a glass envelope attached to a supportin base 2 of insulating material. The envelope I is preferably evacuated and filled with a, suitable gas or gaseous mixture of the character usually employed in rectifier tubes, such as mercury vapor or other ionizable gas, neon, argon, xenon, etc. The base 2 carries the usual terminal prongs 3 for connecting the device with an electric circuit, although a screw base or other manner of attachment might be used, if desired. The envelope I has a reentrant stem 4 terminating in a press 5 of the usual character.

A pair of rigid wires 6, each of which is elec-' trically connected to one of the terminal prongs 3, are embedded in the press 5 in upstanding relation in the envelope 1, substantially in diametrically opposite sides thereof. Each of the wires 6 supports an anode 7 in opposed relation to the other anode. Each anode l is shown as formed of an arcuate plate, with the anodes arranged to be disposed on opposite sides of the cathode assembly that is adapted to be mounted therebetween.

The cathode assembly illustrated as an example, includes filament sections 8 and 9, each of which consists of a strip of nickel ribbon preferably wound in the form of a helix and substantially channel shaped in cross section, such as is set forth more in detail in the patent of Erwin F. Lowry, No. 2,208,467, granted July 16, 1940. This nickel ribbon is preferably coated with alkaline earth oxide, such as barium or strontium oxide.

It will be understood, however, that other cathode constructions may be used if desired, such as a helix made of stranded nickel wire, or a helix made of over-wound nickel wire, or nickel mesh, or even an indirectly heated cathode.

The filament sections 8 and 9, in the form illustrated, are separated from each other by an insulating washer it! formed of suitable insulating material, and having spacer shields H on opposite sides thereof of conducting material, each connected respectively with the adjacent end of the corresponding filament sections 8, 9, and connected together through an opening I2 in the insulator Ill, as indicated at l3 in Fig. 2, to form an electrical connection between the filament sections 8 and 9.

The filament is enclosed within a casing or shield l4, preferably of cylindrical shape as shown in Fig. 5. The insulating washer i0 is arranged approximately midway of the height of the shield I 4 and separates the top half from the bottom half of this shield or receptacle for the filament. The shield or receptacle I4 is closed at the top by a cover plate I5, and substantially closed at the bottom by a cover plate 16, although the latter has an opening ll therein through which the down-turned end 9' of the filament section 9 extends and is joined to a supporting wire 18. A second supporting wire I9 is attached to an eyelet 20, fixed in the bottom it of the cathode receptacle I 4. The wires [8 and [9 are connected at their lower ends with two of the terminal prongs 3 on the base 2.

The filament receptacle I4 is cylindrical, as shown in Fig. 5, and has oppositely directed fins 2! on diametrically opposite sides thereof extending substantially throughout the height of the receptacle, separating the anodes! from each other.

The receptacle or shield I4 is provided also with openings 22 in the respective opposite sides thereof (Fig. 4), which openings 22 are spaced apart lengthwise of the receptacle and disposed on opposite sides of the insulator 10, so as to be located in the respective opposite halves of the receptacle. Thus the opening 22 which faces each of the anodes 1 permits that anode to conduct through the opening from only one of the filament sections. There is, therefore, no ionization present that the other anode can attract during this part of the cycle when it is negative. Moreover, the fins 2| tend to prevent the negative anode from attracting ionization around the outside of the receptacle M. The ionization of the conducting anode is restricted further by the mounting of the anodes I close to opposite sides of the cathode receptacle 14, so that there is no opportunity for ionization to spread to some part of the tube which is not shielded from the negative anode.

I have found from actual use of this tube that cross current is substantially eliminated thereby, due to the construction of the cathode assembly in its relation to the anodes. This gives low gas clean-up and long life. The construction is simple as contrasted with other attempts to accomplish low cross current. Furthermore, the construction is sturdy, having the ability to withstand vibration and jarring without injury thereto.

The device is adapted to be used in the usual manner of a full wave rectifier tube wherein discharge takes place alternately from the respective cathode sections to the corresponding anodes on different parts Of the wave cycle, in a manner that is understood in this art.

I claim:

1. A cathode for an electric discharge device comprising a filament structure having an elongated surrounding shield and adapted to emit electrons to a plurality of anodes located on different sides of the shield, said shield having a plurality of openings in different sides thereof respectively spaced lengthwise of the shield and out of alignment with each other transversely of the cathode structure, said shield being imperforate to electronic transmission at other than said perforated side thereof in the same transverse plane.

2. A cathode for an electric discharge device comprising a filament having an elongated surrounding shield, means separating the space within the shield into different sections, said shield having emitting openings through the surrounding wall thereof on opposite sides of the separating means for electrical discharge to respective anodes from the filament sections, said shield being imperforate to electronic transmission at 4 other than said perforated side thereof in the same transverse plane.

3. A cathode for an electric discharge device comprising an elongated surrounding shield having an insulating partition therein dividing the space within the shield into sections, cathode devices mounted within the shield on opposite sides of the partition, said shield having openings in different sides thereof on opposite sides of the partition for electrical discharge from the cathode devices to respectively different anodes spaced on different sides of the shield, said shield being imperforate to electronic transmission at other than said perforated side thereof in the same transverse plane.

4. A cathode for an electric discharge device comprising an elongated surrounding shield having a transverse insulating partition intermediate the ends thereof, filament sections mounted in the shield on respectively opposite sides of the partition and electrically connected together, said shield having an opening in a side thereof at one side of the partition and a separate opening in a difi'erent side thereof at the opposite side of the partition for electrical discharge from the filament sections through said openings to respectively different anodes, said shield being imperforate to electronic transmission at other than said perforated side thereof in the same transverse plane.

5. A cathode for an electric discharge device comprising a surrounding shield having a transverse insulating partition intermediate the ends thereof, filament sections mounted in the shield on respectively opposite sides of the partition and electrically connected together, said shield having an opening in a side thereof at one side of the partition and a separate opening in a different side thereof at the opposite side of the partition for electrical discharge from the filament sections through said openings to respectively different anodes, said shield having outwardly projecting fins on opposite sides thereof between the openings and extending lengthwise of the shield throughout the length of the circumferential space of the openings to prevent ionization around the outside of the shield.

6. A cathode for an electric discharge device comprising a surrounding shield having an emitter mounted therein, said shield having openings in different sides thereof for discharge from the emitter to respectively different anodes through the openings, and laterally projecting fins on the outside of the shield between the respective openings and extending substantially lengthwise of the shield throughout the space of the openings to prevent ionization around the outside of the shield.

'7. A cathode for an electric discharge device comprising separate sections of helical filament electrically connected together in axial alignment and longitudinally displaced from each other, the convolutions of the respective sections being approximately of equal circumferential extent and the convolutions of one section being spaced apart a greater distance than the convolutions of another section thereof.

8. An electric discharge device comprising two anodes, a cathode between the anodes and including a surrounding shield having two openings in opposite sides thereof toward the respective anodes, said openings being displaced axially of the shield from each other, said anodes being spaced apart laterally of the axis of the shield on different sides thereof, and an emitter within the shield for electrical discharge through the openings to the respective anodes.

9. An electric discharge device comprising two anodes, a cathode between the anodes and including a surrounding shield having two openings in opposite sides thereof toward the respective anodes, said openings being displaced axially of the shield from each other, said anodes being spaced apart laterally of the axis of the shield on different sides thereof, a partition extending transversely within the shield between the respective openings, and filament sections mounted on opposite sides of the partition within the shield for electronic discharge through the openings to the anodes.

10. An electric discharge device comprising a plurality of anodes, a cathode mounted between the anodes and including separate emitting portions adapted for electrical discharge to the respective anodes, said anodes being spaced apart laterally on different sides of the axis of the cathode, and means for controlling the discharge from the cathode portions to the respective anodes and confining said discharge to longitudinally spaced portions thereof.

11. An electrical discharge device comprising an envelope, a cathode having a plurality of axially aligned emitting surfaces, a plurality of anodes spaced laterally of the cathode, and means for shielding the electrical discharge from the cathode surfaces and confining the discharge from the respective portions to the anodes at longitudinally spaced portions of the cathode.

12. A full-wave rectifier comprising an envelope, a cathode having two axially aligned emitting surfaces, two anodes disposed on opposite sides of the cathode, and a shield surrounding the cathode and having openings therein at longitudinally spaced points and respectively at opposite sides thereof for discharge from the cathode to the respective anodes.

13. A full-wave rectifier comprising an envelope, a cathode having two axially aligned emitting surfaces, two anodes disposed on opposite sides of the cathode, and a shield surrounding the cathode and having openings therein for discharge from the cathode to the anodes only at longitudinally spaced points of the cathode and respectively at opposite sides thereof, said shield having outwardly extending partitions on opposite sides thereof between the anodes and between the openings to prevent ionization around the outside of the shield.

14. A full-wave rectifier comprising an envelope, a cathode having axially aligned emitting surfaces, a plurality of anodes spaced laterally of the cathode on different sides thereof, a shield surrounding the cathode and having a plurality of openings spaced lengthwise in difierent sides thereof arranged for electronic discharge from the cathode surfaces to the respective anodes, means mounting the cathode and shield within the envelope, and means laterally outside of the shield for mounting the anodes in the envelope, said last-mentioned mounting means extending downwardly from the anodes externally of the shield throughout the height of the portion of the shield below the point of connection of the mounting means with the anodes.

15. A cathode for an electric discharge device comprising separate sections of helical filament displaced longitudinally from each other and arranged substantially in axial alignment, an insulator interposed between the separate sections and separating said sections from each other, means electrically connecting the sections together, the convolutions of the respective sections being approximately of equal circumferential extent and the convolutions of one section being spaced apart a greater distance than the convolutions of another section thereof.

16. An electric discharge device comprising a plurality of anodes, a cathode mounted between the anodes and including separate emitting portions adapted for electrical discharge to the respective anodes, said anodes being spaced apart laterally on different sides of the axis of the cathode, and a shield surrounding the cathode portions and controlling the discharge therefrom to the respective anodes, said shield having an opening therein between each cathode portion and the respectively different anodes.

17. An electric discharge device comprising an envelope, a cathode having a plurality of axially aligned emitting surfaces, a plurality of anodes spaced laterally of the cathode, and a shield surrounding the cathode and controlling the discharge from the emitting surfaces thereof to the respective anodes, said shield having an opening therein between each of the emitting surfaces and. the respectively different anodes and confining the discharge from the respective portions of the cathode to the anodes.

JOHN H. HUTCHINGS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 18,367 Ruben Mar. 1, 1932 1,105,908 Hughes Aug. 4, 1914 1,603,087 Mackay Oct. 12, 1926' 1,794,283 Fitz Patrick Feb. 24, 1931 2,164,892 Banks July 4, 1939 2,203,639 Smith June 4, 1940 

